The surface wear of the tread in railway wheels is a known phenomenon. The wear results in an increase in cost of operation and a reduction in safety when the train is in motion. In order to mitigate this effect, rail operators must perform maintenance actions in order to preserve the tread profile parameters within the values set by railway norms.
For trains, the parameters have been defined as follows: wheel diameter, diameter difference between vehicle wheels, height and thickness of the flange, indirect measurement of the angle of the flange [qR], difference in profile reduction, difference in area reduction. These parameters determine the degree of wear on the wheel.
In this sense, it is necessary to inspect the condition of wheel profiles on the rolling stock in use, for which prior art has dealt with measurement by way of artificial vision systems, obtaining railway wheel profilograms through devices installed in special setups or on the tracks. In the present invention, rolling stock refers to any device capable of running on a railway.
U.S. Pat. No. 5,808,906 discloses a setup and procedure for measuring parameters on wheels by artificial vision. The document discloses two complementary devices for measuring wheel parameters; a first device is used to capture the transverse profile of the wheel, and a second, to measure the diameter of the wheel. The first device comprises a bearing support, on which the outermost part of the wheel is rolled, so that the tread surface to be measured remains free. On one side of the support, a wheel position sensor is placed, which sends a signal to a flat beam laser generator, which, with the help of a mirror (or with another laser generator), illuminates the entire transverse profile of the wheel. The profile image is captured by a camera equipped with an objective and a filter, and sends the image to an electronic device. The second device has the elements comprising the first device, but differs in that the second device records the image perpendicularly, requiring the wheel to roll on its flange. Therefore, the aforementioned document proposes a measurement procedure with two devices and in two stages; a first stage necessary for measuring the wheel profile, and a second stage, necessary for measuring its diameter. Furthermore, the previous invention discloses a measuring method comprising two different types of modified rail; the first rail is modified so that the wheel rests on its outer tread surface and the wheel profile parameters are found, and the second rail is modified so that the wheel rests on its flange and the diameter is measured. A first drawback of the previous invention is that there is a transition track section between the two types of modified rail, and the need for total modified rail section of great length demands significant intervention on a length of the track. Another drawback of the previous invention is that the measurement of wheel parameters cannot be done simultaneously, and furthermore, the sensors must be dispersed over a considerable length of track. Also, said document claims that the method for measuring the wheel's diameter is done with the wheel resting on its flange on a modified rail, with the help of a guardrail. Therefore, another drawback of the previous invention is that for a vehicle running in such conditions, train guidance on the track is eliminated, i.e. it is already known that the guidance in train motion is affected by the geometrical relation between the rails and the wheels. If such a relation were to be eliminated, a risk of derailment of the vehicle would be generated. Therefore, the previous invention violates the standards and regulations concerning railway vehicle safety. In the previous invention's setup, the use of two measuring devices in a two-phase measurement is inconvenient, as it comprises a complicated implementation, given the elements that belong to each of the measuring phases must be synchronized, and it also requires an extensive modification of the tracks in order to install both devices.
WO2004046644A2 discloses a method and system for measuring railway wheels using multiple light sources to illuminate portions of the wheels' surfaces. This document comprises at least three laser light sources and three cameras properly operating and in a synchronized fashion, recording three images in order to obtain at least one wheel parameter. One drawback of the aforementioned document is that the device has three sets of lasers and cameras that cannot be considered autonomous devices, capable of operating and processing data independently in order to obtain the measurements of the wheel. Obtaining profile data requires an adequate record of all three images in order to have any of the wheel's profile measurements. Additionally, the previous invention comprises a plurality of laser light sources each with a corresponding camera, so that each set records a different portion of the profile of the wheel. Therefore, image processing and the implementation of the system are more complex, and limited to the resolution and data transmission capacity from each camera to the data processor. The complexity in the system and image processing causes a decrease in the sampling frequency of images, turning these drawbacks into loss of precision in measuring the tread of the wheels. Additionally, this document discloses a measurement method comprising the use of calibration data, required for each of the three images from each laser and camera assembly. Therefore, another drawback is that the previous invention requires configuring the relative positions of every camera and its corresponding light source. Furthermore, it is necessary to calibrate the relative position of each camera and light source with respect to the wheels when the images are captured, demanding significant time for calibration.
US2008212106A1 discloses a method for further processing a wheel profile in order to determine wear. The profile data is used as a control variable for controlling a machine for surface machining of the wheel. The invention is characterized by the way the transverse wheel profile is recorded, i.e. by at least three laser devices, which project light beams upon areas that are located on three different sides of the wheel's surface. The previous invention comprises a number of measurements at different places on the wheel, requiring capturing measurements around the entire circumference of the wheel. The aforementioned invention captures the data with the wheel arranged in a lathe-type truing machine, a machining center, or the like. Therefore, a limitation of the previous invention is that the method for obtaining data cannot be performed if the wheel is set on the rolling vehicle on a track at running speed. Furthermore, the previous invention is characterized by the fact that the method comprises starting conditions for recording the wheel. Therefore, a drawback of the prior invention is that each wheel must be positioned on a test bench and meet conditions to start recording wheel data. Additionally, the previous invention is characterized by the fact that the method comprises rotating conditions for the wheel, determined by a set of signals. Therefore, a drawback of the prior invention is that wheel data recording must satisfy specific and controlled conditions during the test.
US2003160193A1 relates to the measurement of the rolling and turning parameters in railway wheels, using optical and artificial viewing techniques to obtain the record of both sides of the wheel. The previous invention comprises two line laser light sources, which must make a single line on the surface of the wheel. One drawback is that the laser light sources cannot be considered independent elements, able to operate independently for obtaining wheel measurements. Each laser light source must be positioned and pointed in a certain direction, and with such precision that the projected lines by each laser light source on the wheel profile satisfy two conditions: one condition is that lines must be arranged collinearly, and the other condition is that the lines must overlap, requiring a complex, precise and robust device assembly, in order to properly position the laser light sources. Furthermore, it is characterized by comprising a periscope consisting of two mirrors, or the like. This is poises a drawback, as it requires a complex and precise device assembly, in order to position the mirrors relative to the projected line on the wheel's surface, and relative to the camera. The previous invention is also characterized in that it uses mathematical algorithms to process a composite image consisting of a profile view of the wheel directly obtained from the camera and a second view acquired by a set of mirrors. The disadvantage is that for obtaining the wheel profile data, it is necessary to process an image with information from two profile sections, whereby both the image processing and the implementation of the data recording system become more complex and generate a loss of precision in measurement.
WO9012720 discloses an apparatus for examining, on the track, the profile of each of the wheels of a passing train comprising a light source positioned to project a line that extends transversely over the surface of the wheel to be captured by a camera. This document is characterized by comprising further means for measuring the diameter of the wheel, which is used to trigger the lighting unit. Additionally, the measuring tools comprise a further light source arranged to illuminate one side of the wheel and an additional camera positioned to capture a part of the rim area of the illuminated side of the wheel.
Other documents closer to the present invention are WO0107308A1, WO2004058554A1, EP1614602A1, which refer to systems for detecting the roundness of railway vehicle wheels, and have mechanical measurement systems that record the circumferential radius of the wheel flange top, based on the fact that the perimeter of railway wheel flanges are precisely round and that the shape of the flange is rarely affected or worn. Therefore, the flange is used as measurement data of the wheel's diameter. The present invention is also based on the measurement of the wheel flange top for obtaining the diameter of train wheels. However, the technological principles on which the prior art devices are based differ from those that have been used for the development of this invention. Moreover, although all these known devices are advantageous for detecting the diameter of the wheel, they do not, however, satisfy the current requirements, given the prior art measures a single parameter of the wheel to determine roundness.
Therefore, the devices and methods of the prior art are limited to the use of cameras for capturing an image thus recording the entire profile of the wheel or wheel diameter. The prior art makes use of a set of digitized images from two or more capturing cameras with two or more laser light sources or array of mirrors and other component images, so that each element captures a different part of the profile. This undoubtedly represents a high processing load on the set of images generated by each device as well as an increase of the complexity for the implementation of the devices. Therefore, there is a need for detection with high accuracy in measuring the geometric parameters of the wheel through a single partial profilogram representing a fraction of the contour of the revolution surface of the wheel, by reconstructing all the information pertaining to the transverse wheel profile recorded by way of image processing by a system able to use a single image from a single camera with a structured light source.